Method and apparatus for measuring physical phenomena

ABSTRACT

A closed loop measuring system includes a digital computer, a measurement device, actuator means associated with the measurement device, and controlled by the computer for establishing known and unknown conditions of a physical phenomena such as pressure, torque, or temperature in the measurement device, and the sensors associated with the measurement device responsive to the conditions established therein for producing relative data values which are stored in the computer memory. The computer controls the establishment of the known and unknown conditions in the measurement apparatus and the storing of the relative data values, and calculates the unknown conditions from the stored relative data values and the stored values for the known conditions. Measurement apparatus for use in such systems, includes a water manometer for measuring gas pressure, a mercury manometer for measuring gas pressure, a torque transducer for measuring torque loads, and a temperature transducer for measuring temperature.

United States Patent Munson et al.

METHOD AND APPARATUS FOR [151 3,657,926 [4 1 Apr. 25, 1972 MEASURING PHYSICAL PHENOMENA Primary Examiner-Donald O. Woodiel Attorney-Giles C. Clegg, Jr. [72] inventors: Robert V. Manson; Richard E. Bensmiller,

both of San Antonio, Tex. [57] ABSTRACT [73 1 Assignee: Thayer Corporation San Antonio A closed loop measuring system includes a digital computer, a [22] Filed: Apr. 2, 1970 measurement device, actuator means associated with the measurement device, and controlled by the computer for [21] APP! 25'162 establishing known and unknown conditions of a physical Related Applicafion Dam phenomena such as pressure, torque, or temperature in the measurement device, and the sensors associated with the meal commuatlon'm-part of 868,833, 23, surement device responsive to the conditions established 1969, abandonedtherein for producing relative data values which are stored in the computer memory. The computer controls the establish- [52] [1.5. Cl. ..73/404, 73/398 C mem of the known and unknown conditions in the measure [51] 7/22 ment apparatus and the storing of the relative data values, and [58] Elem Search 73/420 calculates the unknown conditions from the stored relative 235N513 15134 data values and the stored values for the known conditions. Measurement apparatus for use in such systems, includes a [56] References Cited water manometer for measuring gas pressure, a mercury UNITED STATES PATENTS manometer for measuring gas pressure, a torque transducer for measuring torque loads, and a temperature transducer for 2,203,523 6/1940 Cunningham ..73/404 X measuring temperature 2,620,666 12/1952 Schmidt .73/404 2,818,726 1/1958 Amonette et al. ..73/4 35 Claims, 28 Drawing Figures m T: :I. Il fi w .ll I CONTROL H READOUT l l [4 1;; 2 I I PROCESS SENSOR 1 INPUT MEMORY OUTPUT CONTROL I 2 l l l MEASUREMENT 3 DEVCE l ARITHMETIC r l H 1 UNIT 1 (MEASUREMENT l DEVICE ACTUATORS I l PATENTEDIIPII 25 I972 SHEET UZUF 15 FIG. 2

RESOLVER 53 REsoLvER- TO DIGITAL -/57 CONVERTER PRESSURE 30 MEASUREMENT DEVICE Av/ VALVE B VALVE Cw- VALVE COMPUTER Io 0 VALVE E VALVE FIG. 9

INVENTORS ROBERT v. MUNSON RICHARD E. BENSMILLER ATTORNEY PATENTEDAPRZS I972 I 3. 657. 926

SHEET 030F 15 33 3 4 35 33 34 35 I y x I 33 34 35 l l l4 FIG. 3 FIG. 4 FIG. 5

INVENTORS ROBERT V. MUNSON RICHARD E. BENSMILLER 763M Q z-lgi g x ATTORNEY PATENT EU APR 2 5 I972 RESOLVER READ DV-BL DV-BL ADD RANGE F DV-TL CLOSE VALVE A OPEN VALVE B FIG. IO

SHEET 0% OF 80 READ RESOLVER suRTRAcT DV-I 0v-2- 33 3153} ACOUNT REsbLvER REG DIVIDE 82 A PI (-1 P08 ACOUNTQ CAL-FACTOR NEG I as VZ LSE B 93/ OPEN VALVE D 94/ TIME DELAY READ 85 CLOSE S Y VALVE A 96/ OPEN CLOSE /86 VALVE B VALVE 0 OPEN 87 VALVE A 88 READ RESOLVER ov-z SUBTRACT e9 0v-2 DV-BL REG INVENTORS ROBERT V. MU NS'ON RICH D E. BENSMILLER j% y 9022 I ATTORNEYS PATENTED RZ me 3.657, 926

SHEET 08 0F 15 SIN E COS|NE CONVERTER FIG. I2 FIG. l3

S|NECOS|NE 227 CONVERTER 235 f 2|O\/- PRESSURE MEASUREMENT DEVICE VALVE COMPUTER 20l VALVE 202 VALVE zos VALVE I INVENTORS ROBERT v. MUNSON FIG. l4 RICHARD E. BENSMILLER YWK/ZM ATTORNEY PATENTEDAPR 25 m2 3, 657, 926

SHEET 070i 15 CLOSE VALVES 25o 26|./ TIME 200 a 2m DELAY I 251- 262 READ Bl OPEN STORE DV|3 VALVES I00 5. lOl

I DIVIDE (PlZ-Pll) TIME fzsz zezs wv l2- ovu) DELAY 9FACTOR READ a MULTIPLY STORE DVH ,253 g54-/ (x) FACTOR a ma CLOSE VALVE 20: w 254 i EXIT OPEN J 255 VALVE 202 I READ DATA J 256 VALUES CONTACT 204 BEEN MADE s'romg 0v l2 J 258 CLOSE 5 VALVE 202 q f INVENTORS OPEN 250 VALVE 20.3 ROBERT MUNSON I F I RICHARD E. BENSMILLER ATTORNEY FIG. 16

mvENTORs ROBERT v. MUNSON {RICHARD E. BENSMILLER ATTORNEY PATENTEDAPR25|912 sum near 15 POTENTIOMETER DYNAMOTOR TO DIGITAL CONVERTER 35s I I DYNAMOTOR' LOAD CONTROL L RPM PICK-OFF COMPUTER DEVICE TORQUE PICK-OFF DEVICE I 334 FIG, I9

ROBERT vfmulyson RICHARD E. B'ENSMILLER FIG. l7

mvENToRs ATTORNEY PATENTED RZ IBYZ 3.651926 SHEET 100F 15 T NO-LOADY 36I READ RPM a TORQUE COUNT IS LEVEL COUNT [00 YES STORE RPM COUNT RV 3| I ADDITO LEVEL COUNT STORE TORQUE 363 COUNT TV3I 3?: l INCREASE 3s4 I LOAD DECREASE I I L AD SET LEVEL I COUNTER A TO ZERO 7 J sToRE' RPM COUNT RV32 READ RPM 366 a TORQUE 373 I COUNT V STORE TORQUE COUNT TV 32 3s? TORQUE ARM YES LEVEL F K3. 2O

YES TORQUE ARM HIGH Y 'imvEmcRs I ROBERT v; MUNSON RICHARD E. BENSMHLLER ATTHHNF' PATENTEnmzs I972 3.6 57. 926

SHEET 110! 15 374v SET RPM B 4 READ RPM COUNTER a BITORQUE TORQUE coumea coum TO ZERO STORE RPM 375 385/ coum vss SENSE OFF I MAGNET w STORE TORQUE aas coum TVSB 31s COMPUTE k. START P 387 (RPM smRv 3|) COUNTER aw-3a 377' auaa I OFF COMPUTE MAGNET TVBB-TV 3| To 32 :TQ 33- STOPRPM COUNTER EXIT START TORQUE COUNTER OFF MAGNET T FIG. 22 9, STOP TORQUE COUNTER IINVENTORS F'lG.-2l ROBERT v. muusou I RICHARD E. BENSMILLER PATENTED PR 25 m2 3, 657. 926

SHEET 13UF 15 OHM A OHM FIG-p 25 OHM 2 SAOHM E OHM 20 2 Ll-I L: B

OHM 2b 2 3 g HOHM ,2-3,-4, 4o 4 5 6 l1 NOTCH OHM 4b 7 7 w A OHM N A OHM c U Z OHM 4c g s 2 8 DC READ a STORE PROCESS OHM CALCULATE 5 (M43) x (x) INVENTORS I ROBERT v. MUINSON RICHARD E. BENSMILLER ATTORNEY PATENTEDAPR 25 I972 3.657. 926

SHEET 1 0F 15 436 STORE av 42 READ 8; STORE f PROCESS OHM 438 READ OHM TuRN ON HEATER COMPARE OHM DV- LO 439 READ OHM COMPARE OHM DV -Hl 'TURN OFF F G 6 HEATER I 2 IDENTIFY NOTCH 433v STORE WMWIBEM M INVENTORS 435 NOTCH ROBERT v. MUNSON RICHARD E. BENSMILLER ATTORNEY PATENTEDAPR 25 I972 3 657', 926

sum 15 0F 15 445 READ 0 HM 454 TIME 446 455 DELAY BELT? READ OHM 4 SUBTRACT COMPARE (OHM 3 457 OHM 2: (OHM 4 J av 43 A OHM N SUBTRACT 449 COMPARE (OHM A OHM-1N; (OHM 2) A OHM A OHM 4 459 ADD ADD (A 0mm (OHM a) (4A OHM) (OHM 4) s! iA OHM El ADD 45l' ADD (SIGMA)+ u) SIG I) 2 460 SIGMA S|G l J DIVI DE 452 I (sA OHM) DIVIDE A2 OHM OHM J COMPARE I AOHM 5 OHM EXIT ROBERT V. MUNSON RICHARD E. BENSMILLER ATTORNF REFERENCE TO RELATED APPLICATION This application is a continuation-in-part of application Ser. No. 868,838, tiled Oct. 23, 1969 now abandoned.

BACKGROUND OF THE INVENTION This invention relates to measuring physical phenomena under the control of a computer wherein .the computer controls the establishment of known and unknown conditions in a measurement-device, receives from the measuring device relative data values correspondingto such known and unknown conditions, and calculates the measured values of the unknown conditions.

ln applications where it is important that measurements of pressure, temperature and torque, for example, be quite accurate, it is necessary to frequently calibrate the measuring instruments or devices against known standards. Frequently the techniques forcalibrating such measurement instruments are time consuming and, therefore, expensive; additionally the calibration techniques may require interruption of process streams or the operation of apparatus.

The calibration of gas pressure measuring instruments, for example, is usually done with gage blocks, thermometers, and the local value of gravity; theseprocedures being involved and time consuming. The calibration of pressure measuringinstruments which are on-line in a processing stream may present particular problems since it may be necessary either toremove the instrument from the line or to connect aprimary standard in the line. A particular problem would exist in the on-line situation where the pressure measuringinstrument is continuously monitored to assure proper process control, or even more particularly where the value of the continuously measured or monitored pressure is employed toproduce a control signal which varies or controls a further process function in response to pressure variations. ln-such a situation where the pressure control process function is quite criticaL-the suspicion of inaccuracy in a pressure measuring instrument may 7 prompt the decision to shut downtheprocess stream.

The measurement of process temperatures is usually accomplished with thermocouples, with the thermocouples being calibrated'by charting the thermocouple outputsfor a known temperature as measured by a thermometer for example. The disadvantages of thermocouple measurement devices include inaccuracies due to corrosion, and difficulty of calibration due to inaccessability of the thermocouples in process equipment. Another disadvantage, in regard to calibration, isthat it may be necessary to remove the thermocouples from the process locationdueto the fact that the process stream will not withstandthe calibration temperature involved. Anothermethod of calibrating temperature measuring instruments in process situation is toplace a primary standard on-line and compare the output of the on-line measuring device with the primary standard. This procedure is time consuming and may involve shut down of theprocess stream.

The measuring or monitoring of torque loads come either in a test situation or under operation conditions usually performed through the use of a torqueshaft with strain gages attached. The procedure is involved and time consuming and particularly in that after the strain gages are appropriately affixed to the torque shaft, the torque shaft strain gage instrument must be calibrated by chartingthe output of the instrument known as torque loads as measured with a dynamometer for example.

It would be very desirable then tohave available instruments for measuring physical phenomena which may be calibrated very accurately and very quickly, and particularly against known conditions whichare inherent conditions measured by the apparatus and which exist at the time of taking the measurements of theunknown conditions. This invention is concerned with a method and apparatus for taking measurements of pressure, temperature and torque and where the measuring instrument may be readily recalibrated if it is suspected that the extent calibration is no longer valid.

SUMMARY OF THE INVENTION calculating the value of the unknown condition from the measured values of the known conditions and the outputs of the transducer measuring instrument.

Another object of thisinvention is to provide a method and apparatus for measuring a physical phenomenon, wherein known conditions ofthe phenomenon to be measured are employed as constants to calibrate a measuring instrument and also to calculate the values of the unknown conditions of the phenomenon established by the measuring instrument.

Another object of this invention is to provide a method and apparatus .for measuring a physical phenomenon, providing for self-calibration 'of the measuring instrument with minimal interruption of the phenomenon to be measured which are established in the measuring instrument.

, Another object of this invention is to provide a method and apparatus for measuring a physical phenomenon providing self-calibration of the measuring instrument with minimal interruption of the measuring function.

A further object of this invention is to provide a method and apparatus for providing data corresponding to known and unknown conditions of a physical phenomenon from which the value of an unknown condition of the phenomenon can be mathematically determined.

Broadly, a method according to the invention includes establishing at least two known conditions of a phenomenon to be measured in apparatus for measuring that phenomenon,

establishing at least one unknown condition of that phenomenon in the apparatus which is the condition to be measured, and storing relative data values in a memory for each of these established conditions, the relative data value being one coordinate of different points on the curve and the measured values of the known conditions being the other coordinates of respective points whereby the value of the unknown condition may be mathematically calculated using curve fitting techniques. The method further contemplates providing a computer including a memory, a control means, and a processing means, whereby the computer controls the establishment of the several conditions in the measurement apparatus, accepts and stores the relative data values corresponding to the established conditions, and calculates the value of the unknown condition. The measuring process, then,

involves self'calibration of the measuring instrument against the known conditions.

Apparatus according to the invention includes a measuring device for measuring a certain physical phenomenon, the device including actuators for establishing different conditions of the phenomenon therein, and including a sensor for from the following description when read in connection with the accompanying drawings.

DRAWINGS.

FIG. 1 is a block diagram of a closed loop computer controlled measurement system including a measurement device such as a pressure measuring instrument, a sensor for detecting information to be used by the computer in its control function, and measurement device actuators which are controlled by the computer;

FIG. 2 is a diagrammatic illustration of a water manometer pressure measuring device for use in a computer controlled system as depicted in FIG. 1;

FIGS. 3 through 8 are diagrammatic illustrations of different operating conditions of the apparatus of FIG. 2;

FIG. 9 is a functional block diagram of a computer 'controlled system including the apparatus of FIG. 2;

FIGS. 10 and 11 are flow charts for use in preparing a computer program for the operation of the system of FIG. 9;

FIG. 12 is a diagrammatic illustration of a mercury manometer pressure measuring device for use in a computer controlled system as depicted in FIG. 1;

FIG. 13 is a schematic circuit diagram including certain circuit components illustrated in FIG. 12;

FIG. 14 is a functional block diagram of a computer cntrolled systemincluding the apparatus of FIGS. 12 and 13;

FIG. 15 is a flow chart for use in preparing a computer program for the operation ofthe system of FIG. 14;

FIG. 16 is a diagrammatic cross-sectional view of a torque transducer for measuring torque in a computer control system as depicted in FIG. 1;

FIG. 17 is a transverse sectional view taken along the line 17-17 ofFIG.16;

FIG. 18 is a perspective view of a dynamotor for use with the torque transducer of FIG. 16;

FIG. 19 is a functional block diagram of a computer controlled system including the apparatus of FIGS. 16 through 18;

FIGS. 20, 21, and 22 are flow charts for use in preparing a computer program for the operation ofa system of FIG. 19;

FIG. 23 is a combination diagrammatic illustration and block diagram, diagrammatically illustrating a temperature transducer for use in a computer controlled system as depicted in FIG. 1 and illustrating in block diagram a computer controlled temperature measuring system;

FIGS. 24 and 25 are curves illustrating the operation of the temperature measuring system of FIG. 23; and

FIGS. 26, 27, and 28 are flow charts for use in preparing a computer program for the operation ofthe system of FIG. 23.

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIGURE 1 is a block diagram of a closed loop computer controlled system for measuring physical phenomena, such as absolute pressure or pressure differentials wherein information or data from the measurement device, such as a pressure measuring device to be described, is transmitted to the computer input. The data is processed and transferred at the computer output in a form to be used, such as a printed record or as signals for controlling other apparatus. Additionally, the measuring device is controlled by the computer output to perform measurements of known and unknown conditions of the phenomena to be measured; and this is done through control of actuators associated with the measurement device operated by the computer output.

Referring to FIGURE 1, a computer includes a central processing unit which is made up of a control unit 11, a memory unit 12 and an arithmetic unit 13. The input unit 14 converts the data received from the measurement device into appropriate form for handling by the central processing unit; and the output unit converts the output from the central processing unit to a form suitable for desired use. The desired form of output data may be printed information produced by a readout unit 16 or electric signals for use in a process control unit 17.

A measurement device 20 includes actuators 21 for controlling its operation, the actuators being operated by the computer output unit 15 to perform the desired measurement functions. The measurement device sensor 22 senses or detects the changes in physical phenomena and transmits information to the computer input 14.

In the specification which follows, there are described four separate and distinct systems for the practice of the method of the invention, each system including apparatus for the measurement of a particular physical phenomenon which apparatus is disclosed for use in combination with a digital computer. The apparatus and systems described include a water manometer measuring device for use in a gas pressure measuring system, a mercury manometer measuring device also for use in a gas pressure measuring system, a torsion bar transducer device for use in a torque measuring system, and a temperature transducer probe device for use in a temperature measuring system. For each of the above mentioned systems flow charts are illustrated and described, by way of example, which might be used in the preparation of a computer program for the operation of the respective measurement apparatus and systems and for the practice of the method according to the invention.

WATER MANOMETER PRESSURE MEASURING SYSTEM One form of apparatus for practicing the method of the invention includes a water manometer pressure measuring instrument shown in FIGS. 2 through 9.

FIG. 2 is a diagrammatic illustration of measuring apparatus for use in a computer controlled system as illustrated in FIG. 1 and described above. Referring to FIG. 2, a measurement device 30 includes a vessel 31 for containing a pool of liquid 32, such as water, the vessel 31 being shown in the form of a closed vessel and adapted to be either pressured or evacuated to provide a reference pressure within the vessel which differs from atmospheric pressure. Additionally, the closed vessel may be pressurized with a gas other than air which is to be measured, either at atmospheric or other pressure. In the preferred embodiment, the reference pressure is atmospheric pressure which may be provided in the vessel chamber by opening the valve E to vent the chamber to atmosphere. While the following description refers to the measurement of air pressure, it will be understood that the pressure of other gases may be measured in the same manner.

A float 33 is disposed within the vessel for vertical movement in the liquid, the float taking the form for example, of an inverted cylindrical cup defining chambers 34 and 35 which are concentric about a vertical axis. The cylindrical inner chamber 34 will be referred to hereafter as the pressure chamber, while the annular outer chamber 35 will be referred to as the ballast chamber. The bottoms of both chambers are open to communicate with the liquid 32 within the vessel, with the bottom edges or skirts of the chamber walls lying in a common plane. The float is guided for vertical movement as will be described. The float may be fabricated of any suitable material which is heavier than the liquid in which it is immersed.

In its lowermost position within the vessel 31, the float rests on the bottom of the vessel. This position is illustrated in FIG. 3 of the drawings which also indicates the normal level of the liquid 32, this level lying somewhat below the top of the float in its lowermost position. The float may be supported in its lowermost position by circumferentially spaced bosses 36, for example, to permit the free flow of liquid from the vessel chamber into the chambers 34 and 35, when desired. The upper portions of the float chambers 34 and 35 then define closed pockets of which are closed by the liquid 32. The chambers 34 and 35 then contain two vertical columns of water, the heights of which are controlled by the air pressures in the closed pockets ofthe chambers.

A stand pipe 38 extends upward through the bottom wall of the vessel 31 defining a conduit for communicating the closed portion of the pressure chamber34 with the vessel 31 above the liquid pool and with other sources of pressurized air as will be described. Similarly, a stand pipe 39 extends upwardly through the bottom wall of the vessel 31 defining a conduit for communicating the closed portion of the ballast chamber 35 with the vessel 31 above the liquid pool and with other sources of pressurized gas as will be described. The upper ends of these conduits are always above the liquid level within the chambers to control the air pressures within these chambers,

The conduit 38 communicates through a valve D with a conduit 40 which opens through a port in the side wall of vessel 31 to the vessel chamber above the liquid leveLWhen the valve D is opened, thepressure within the pressure chamber 34 is equalized with that in the vessel chamber which acts on the top of the float 33. Through a branch conduit 41 and a valve C, the conduit 38 is selectively. communicatedwith an unknown pressure to be measured by the apparatus.

The conduit 39 for the ballast chamber 35 is communicated through a valve A with the conduit 40, so that the pressure in this chamber may also be equalized, when desired, with the reference pressure within. the vessel chamber. Through a branch conduit 42 and a valve B, the ballast chamber is selectively communicated with a source of pressurized gas which is more than sufficient to lift the float 33 to the upper limit of its excursion, wherein the lower edges of the float chamber walls are adjacent to the upper surface of the liquid.

The valves A, B, C, D, and E may be solenoid operated to on or off" conditions, and are the measurement device actuators 21 of FIG. 1 which are controlled by the computer output.

For the purpose of detecting and measuring the vertical excursion of the float 33, a form of parallelogram linkage device 45 is provided consisting of upper and lower horizontal arms 46 and 47 which extend through the vessel wall and are pivoted to the wall by means of sealed hinges 48 and 49 respectively; and a vertical leg 50 pivoted at hinges 51 and 52 to the horizontal arms 46 and 47 respectively. The leg 50 is rigidly attached to the top of the float by means of a coupler 56 to follow the vertical movements of the float and also to guide the movements ofthe float.

A rotary resolver or synchro 53 is mounted on the exterior of the vessel 31 and includes a drum 34 driven by a wrapped cable 35 which is secured between the arms 46 and 47. It will be seen that the parallelogram linkage and resolver provide electrical data values which are responsive to the vertical excursion of the float; and these data values may be converted by means of a resolver-to-digital converter to digital values acceptable by the computer input unit. The parallelogram linkage, the resolver, and the resolver-to-digitalconverter, then comprise the sensor 22 of the system of FIG. 1. The computer may be programmed to perform a measurement operation and a calibration operation of the measurement device 30, by controlling the several values to produce desired conditions within the pressure and ballast chambers, with the program being responsive .to the input information received from the sensor components and to predetermined information stored in the computer memory. With computer control, the instrument calibrates itself at any time through initiation of the calibration program.

FIG. 9 is a functional block diagram of the measurement apparatus and computer, illustrating a closed loop' system wherein the several actuator valves A through E of the measurement device 30, which may be solenoid operated valves for example, are controlled by the output of the computer in response to input from the sensor components including the resolver 53 and a resolver-to-digital converter 57. FIGS. 3 through 8 are diagrammatic illustrations relating to FIG. 2 which show different relative positions of the float 33 and vessel 31 and relative liquid levels, which will be referred to in the foregoing description of operation.

The operation of the system will now be described, first the operation in connection with the calibration of the pressure measuring instrument, then the operation in connection with measuring and computing the unknown pressure. Reference will be made to FIGS. 3 through 8 which illustrate diagrammatically the relative positions of the float within the vessel, and the relative liquid levels within the vessel 31 and the chambers 34 and 35. Reference will also be made to FIGS. 10 and 11 which are flow charts which may be used to program a computer to perform the operations described. The flow chart diagrams are numbered for reference.

It is assumed that the system is to be calibrated for the measurement of air pressure with atmospheric pressure being the reference pressure within the vessel 31; and accordingly the valve E is opened. Valves B and C are closed, and valves A and D are opened to communicate both the pressure and ballast chambers with atmosphere through the conduits 38, 39, and 40. The float, being heavier than water, will sink to the bottom of the vessel; and time is allowed for the float to sink and for the water levels to equalize in the ballast and pressure chambers (Flow chart diagrams through 75.) This condition of the float is illustrated in FIG. 3. The parallelogram device 45 follows the float; and when the float reaches the bottom of the vessel, the resolver produces the data value DV-BL which identifies the bottom limit of float excursion. This data value DV-BL is stored in the computer memory for reference, to ascertain during later operations that the float is not resting on the vessel bottom (Flow chart diagram 76.)

From the design of the measuring device the maximum height to which the float may rise from the vessel bottom is knownand the corresponding range of the resolver count, referred to as RANGE-F, has been predetermined and stored in the computer. The count RANGE-F, when added tothe data value DV-BL, establishes a data value DV-TL which identifies the top limit of float excursion (Diagram 77).

Valve A is now closed and valve B is opened to communicate the ballast chamber with air at a high pressure which is more than sufficient to raise the floatto the top limit of excursion. While the float is rising, the computer monitors the resolver readings, by making successive subtractions of the increasing resolver values with the data value DV-TL. Each difference value is stored in a register, and when the difference value becomes negative, valve B is closed by the computer and time is allowed for the water to settle to a static condition (Diagrams 78 through 84).

The float is now supported by the air trapped in the ballast chamber, with a small portion of the chamber skirts or walls extending below the surface of the liquid, as shown in FIG. 4. The valve D has remained open so that the pressure within the pressure chamber is atmospheric pressure. This is a first known pressure P1, a value for which has been stored in the computer. The resolver is now read and the data value DV-l is stored in the computer memory, this data value DV-l being a function of atmospheric pressure P1. This data value DV-1 also represents the top limit of float excursion which should not be exceeded by the instrument during subsequent operations (Diagram 85).

To obtain a second data value corresponding to a second known pressure, the valve D is closed to trap the air within the pressure chamber, which is now at atmospheric pressure; and the valve A is opened to vent the ballast chamber to atmosphere (Diagrams 86 and 87). The float will now sink until the air pressure within the pressure chamber increases sufiiciently to support the weight of the float distributed over the 7 surface area of the liquid within the pressure chamber. This condition is shown in FIG. 5. The air within the pressure chamber is now the sole support of the float (neglecting the displacement of water by the skirt of the float). The cross-sectional area of the pressure chamber is uniform and is known, as is the weight of the float, and from these the pressure P2 within'the pressure chamber is known by computation; and a value forPZ has,been stored in the computer memory. The resolver is now read and the data value DV-Z which is a function of the known pressure P2 is stored in the computer memory (Diagram 88).

Flow chart diagrams 89 and 90 are concerned with testing to determine that the float has not dropped to the lower limit of excursion represented by data value DV-BL. Data value DV-BL is subtracted from data value DV-2 with the resultant value placed in a register to determine whether it is negative or positive. If the resultant value is zero or negative, the float is resting on the bottom of the vessel and the data value DV-2 is invalid. The computer will be halted and it will benecessary to increase the volume of the liquid 32 and to restart the calibration process.

From the two values of known pressures P1 and P2 and the two corresponding data values DV-l and DV-2, a curve of known slope is established from two points, each point having a known pressure value as one of-its coordinates and the corresponding data value as the other of its coordinates.

Flow chart diagrams 91 and 92 are concerned with calculating a calibration factor (CAL-factor) which is used in the later computation of the unknown pressure. The data value DV-2 is subtracted from data value DV-l to obtain the difference value, referred to as A Count which is stored in the computer. APl, which has been stored in the computer, is the known pressure difference between the known pressures P2 and P1. The value API is divided by the value A Count to obtain the CAL-factor which is the resolver count per unit of pressure change. This CAL-factor is stored in the computer memory.

The next phase of the operation cycle is to locate the float at a predetermined desired level within the range of its excursion for the purpose of accommodating the range of pressures which are to be measured. If the pressures to be measured are near the maximum for which the instrument is designed, the start position of the float should be near the lower limit of excursion. Conversely, if only negative pressures are to be measured it would be desirable to place the start level near the top limit of float excursion. If desired, this phase of operation may be started independently of the preceding steps of the calibration operation.

Since the position of the float at the beginning of this phase of calibration may not be known, the float is allowed to sink to the bottom of the vessel, then raised to the top limit of excursion and then allowed to drop to the pro-selected start level. Valve D is opened to permit the float to sink to the bottom of the vessel with valve A being already open, and sufficient time is allowed for the sinking of the float and for the water level to stabilize within the pressure and the ballast chambers (Diagrams 93 and 94). Valve A is then closed and valve B opened to admit high pressure air to the ballast chamber, and the float rises until the valve B is closed by the computer when the float reaches the top limits as indicated when the resolver reading exceeds the data value DV-TL (Diagrams 95 through 100).

The height of the float for the beginning of the pressure measuring operation is predetermined, and a corresponding resolver count value R2 has been stored in the computer. This value R2 is added to data value DV-BL to determine the data value DV-S which represents the pro-selected float height (Diagram 101). The valve A is now opened to allow the float to sink. The computer now reads the resolver and makes successive subtractions of DV-S from the resolver reading (Diagrams I02 through 105). When the difference becomes negative, the computer closes the valve A so that the volume of air within the ballast chamber is trapped, and movement of the float halts'when the pressure within this chamber is sufficient to support the float. Time is allowed to permit the float to stabilize on the liquid; then the resolver is read and the data value DV-3 is stored in the computer memory (Diagrams 106 through 108). Since the valve D is open, the pressure within the pressure chamber 34 is atmospheric; and the data value DV-3 is a function of atmospheric pressure P1, which is the reference pressure for the computation of an unknown pressure to be measured. This position of the float is indicated in FIG. 6 ofthe drawing.

Valve D is now closed to seal the pressure chamber from atmospheric pressure,-and valve C is opened to communicate the pressure chamber with the unknown pressure which is to be measured (Diagrams 109 and 110). The calibration is completed and the apparatus is conditioned for the measurement of unknown pressures.

FIG. 11 is a flow chart for a computer program concerned with the operation of reading and computing of an unknown pressure.

When the unknown pressure is admitted to the pressure chamber, the float will rise if the unknown pressure is greater than atmospheric pressure; this condition being illustrated in FIG. 7. This unknown positive pressure will increase the gas volume of a pressure chamber with a corresponding decrease of the water volume. As the float rises, the liquid column within the ballast chamber rises with the float above the liquid level in the vessel In this manner the effective weight of 'the float is increased and the buoyancy decreased, and the float height is attained wherein the float is supported by the unknown pressure. The resolver is now read and data value DV-4 corresponding to the unknown pressure is stored in the computer (Diagram If the unknown pressure is a pressure less than atmospheric, the column of liquid in the pressure chamber will rise to increase the weight of the float, causing the float to sink within the liquid pool 32 whereby the effective buoyancy is increased. Again, a stable level of the float will be achieved which is a function of the negative unknown pressure and the data value DV-4 is stored in the computer (Diagram 120). This condition is shown in FIG. 8.

To assure that the data value DV-4 is a valid reading, the computer makes a check to determine that the computer has not moved to or beyond either the top or bottom limits. First, the computer tests to determine that theresolver data value DV-4 does not exceed the top limit data value DV-l (Diagrams 121 and 122). Next, the computer makes a comparison to ascertain that the resolver data value DV-4 is not less than the bottom limit data value DV-BL (Diagrams 123 and 124). Passing both of these tests, the data value DV-4 is a valid function of the unknown pressure P3.

The computer then calculates the difference between the unknown pressure data value DV-4 and the atmospheric pressure data value DV-3 to compute the data value count ADV corresponding to the pressure difference, that is the pressure increase or the pressure decrease from the reference pressure Pl (Diagram 125). The computer then multiplies the count ADV by the CAL-factor to determine the pressure difference AP2 between atmospheric pressure P1 and the unknown pressure P3, from which the unknown pressure is determined (Diagram 126).

From the above description of the apparatus and its operation, it is seen that the apparatus is adapted for the practice of a method of providing data from which the measured value of an unknown air pressure can be mathematically determined and which includes the establishment of known pressures within the apparatus for the purpose of calibrating the apparatus; The method which is described in detail in the above description of operation includes the steps establishing a first known pressure P1, which is atmospheric pressure, in the measurement device; and storing the pressure P1 and a corresponding data value DV-l in the computer memory; establishing a second known pressure P2 in the measurement device and storing this pressure P2 and a corresponding data value DV-2 in the computer memory; these values Pl, DV-l and P2, DV-2 respectively comprising coordinates of points which define a curve of known slope from which the calibration factor is determined; again establishing atmospheric pressure P1 in the measurement device and storing a corresponding data value DV-3 in the computer memory, the values P1 and DV-3 defining the coordinates of a point on a curve having the same slope as that of the first mentioned curve; establishing an unknown pressure in the measurement device and storing a corresponding data value DV-4 in the computer 

1. A method of providing data from which measured values of physical phenomena can be mathematically determined using a curve fitting technique that comprises the steps of: establishing n+1 conditions in a measurement apparatus in response to physical phenomena having n+ 1 known values; establishing a certain condition in the measurement apparatus in response to a physical phenomenon having an unknown value; said measurement apparatus generating relative data values which are a function of the conditions present in said apparatus; storing relative data values in a memory each time a condition is established; and utilizing said n+ 1 known values of said physical phenomena and said unknown value of said physical phenomenon as one coordinate of different points on a curve of n degree, and utilizing the respective stored relative data values as the other coordinate of each of said points.
 2. A method as set forth in claim 1 including the steps: storing in the memory said known values of said physical phenomena; and computing from said stored values and relative data values the unknown value for said physical phenomenon in response to which said certain condition was established in the measurement apparatus.
 3. A method as set forth in claim 1 wherein two conditions are established in the measurement apparatus in response to physical phenomena having two known values; and wherein said two known values and said unknown values are each one coordinate of different points on a first degree curve.
 4. A method as set forth in claim 1 including the steps: providing a measurement apparatus which is responsive to the physical phenomenon to be measured; providing actuator means for said measurement apparatus for establishing in said apparatus the different conditions in response to the phenomena; providing sensor means for said apparatus whose output is the relative data values which are functions of the conditions present in the apparatus.
 5. A method as set forth in claim 4 including the step: providing a programming means for controlling said actuator means in response to the outputs from said sensor means.
 6. A method as set forth in claim 4 wherein said measurement device provided is a U-tube mercury manometer for the measurement of gas pressures; and wherein said sensor means provided is a conductive probe coacting with the liquid mercury in said manometer, and whose output is relative data values which are functions of the height of the liquid mercury in the manometer.
 7. A method as set forth in claim 6 wherein said sensor means provided further includes a conductive probe having a dielectric coating, to define with the mercury liquid a variable capacitor whose output is a function of the height of the mercury.
 8. A method as set forth in claim 4 wherein the measurement device includes a torsion bar for connection with driving and driven member and which deflects rotationally in response to a torque load; wherein the sensing means provided includes a pair of signal producing means mounted for rotation respectively with the driving and driven ends of the torsion bar, signal detection means for detecting signals from the respective signal producing means, and counter means controlled by said signal detecting means for producing a time value which is the function of the deflection torsion bar.
 9. A method as set forth in claim 8 wherein said actuator means provided includes a dynamometer for establishing selected known torque loads at the driven end of said torsion bar.
 10. A method as set forth in claim 4 wherein said measurement device proviDed includes a torsion bar for coupling between driving and driven devices and which deflects rotationally in response to the applied torque load; wherein said sensor means includes a magnet mounted at each end of the torsion bar for rotation therewith in a path spaced from the axis of rotation, a detector mounted adjacent to the path of each of said magnets for detecting the magnetic field of each path of the magnet, and counter means for producing a time count between the passage of said magnet means which is the data value responsive to the deflection of said torsion bar.
 11. A method as set forth in claim 4 wherein said measurement apparatus provided comprises a temperature detecting head including two materials of known ice point, and a thermal responsive device for producing output signals responsive to the temperature of said detecting head; wherein said actuator means provided includes means for heating said head above the temperature of the highest ice point; wherein said known physical conditions are established by heating said head to a temperature above the highest ice point, and detecting the thermal responsive device output as a function of time to identify the relative data values which are a function of the respective ice point temperatures; and wherein said sensor means comprises said thermal responsive device.
 12. A method as set forth in claim 4 wherein said measurement device provided comprises a float supported in a liquid pool and defining with the liquid surface a variable volume chamber, and including means for communicating said chamber with sources of gas for the measurement of gas pressures; and wherein said sensor means provided comprises means for detecting the height of the float under different conditions of pressure, the height of the float being a function of the pressure within the chamber.
 13. A method as set forth in claim 4 wherein said measurement device provided comprises a float of known weight supported in a liquid pool and having an open bottom ballast chamber and an open bottom pressure chamber of known cross-section in communication with the liquid; and wherein said sensor means provided comprises means for detecting the height of the float, the height being a function of the pressure within the pressure chamber; including the further steps: independently supporting said float by communicating said pressure chamber with air at known atmospheric pressure, and detecting the float height as a first data value which is a function of atmospheric pressure; trapping the atmospheric air in the pressure chamber to support the known weight of the float, and detecting the float height as a second data value which is a function of the second known pressure; said atmospheric and second known pressures and said first and second data values determining a ratio of pressure change to data value change; trapping a pocket of air in said ballast chamber to support said float while communicating said pressure chamber with atmospheric air, and detecting the float height as the third data value which is also a function of atmospheric pressure; trapping the air contained within the ballast chamber to retain the extant volume of liquid within said ballast chamber; communicating said pressure chamber with an unknown gas pressure while maintaining said trapped air pocket in said ballast chamber, and detecting the float height as a fourth data value which is a function of said unknown pressure; the difference between said third and fourth data values multiplied by said ratio determining a difference between atmospheric pressure and said unknown pressure.
 14. A method as set forth in claim 1 for providing data from which measured values of torque can be mathematically determined, including the steps: establishing by means of a dynamometer two known torque loads in a driven torsion bar; measuring the angular deflection of said torsion bar by detecting the time different between signals produceD by signal devices mounted in axially spaced relation on said torsion bar, said time differences being functions of the respective torque load; storing said time differences as relative data values of the known torque loads; detecting and storing the angular deflection which is a function of an unknown torque load in the same manner.
 15. A method as set forth in claim 1 for providing data from which measured values of temperature can be mathematically determined including the steps establishing two conditions responsive to known temperature phenomena in a measurement apparatus comprising a temperature detecting probe including a thermal responsive device and two materials having different known ice points; producing relative data values which are functions of the two known ice points by heating said probe to a temperature above that of the highest ice point, and monitoring the thermal responsive device output as a function of time while the probe cools to a temperature below that of the lowest ice point whereby the thermal responsive device output values corresponding to the respective known ice points are detected.
 16. A method as set forth in claim 15 wherein the thermister output values for the respective ice points are detected by calculating output value changes for successive discrete increments of time; and comparing succeeding incremental changes with preceeding incremental changes to detect a change in the cooling rate which is a function of the changing condition of one of said materials.
 17. A method as set forth in claim 1 for providing data from which measured values of gas pressure can be mathematically determined, including the steps: establishing two conditions responsive to pressure phenomena in a U-tube mercury manometer, which pressure phenomena are known from the observed relative height of the mercury in the manometer legs; producing relative data values which are functions of the mercury height, by means of one or more conductive probes in the manometer legs which coact with the conductive mercury and an electric circuit to produce an output signal responsive to the mercury height; and storing relative data values produced by means of said conductive probe each time a condition is established in the manometer.
 18. A method as set forth in claim 1 for providing data from which measured values of gas pressure can be mathematically determined, including the steps: establishing two conditions of known pressure in a variable chamber defined by a floating chamber means and its supporting liquid surface; and producing relative data value which are functions of the height of said chamber means relative to the liquid surface.
 19. A method as set forth in claim 18 wherein a first known pressure condition is established by communicating said chamber with atmospheric pressure while independently supporting said float in said liquid pool; and wherein a second known pressure condition is established in said chamber when said chamber means of known weight is supported in said liquid pool by the volume of air trapped in said chamber to establish said first condition.
 20. A method for mathematically determining measured values of physical phenomena using curve fitting techniques comprising the steps: establishing n+ 1 known physical conditions inherent in a measurement apparatus which is responsive to the physical phenomenon to be measured and the output of which is relative data values which are a function of a condition present; storing values in a memory for each of said known physical conditions; establishing an unknown physical condition inherent in the measurement apparatus; storing relative data values in a memory each time a known or unknown physical condition is established; and computing from the values and the data values stored in the memory a value for the unknown physical condition established in the apparatus; said values for said n+ 1 known physical conditions and said unknown physical conditions each being one coordinate of different points on a curve of n degree; the other coordinates of each of said points being the respective stored relative data values.
 21. In a system including a computer having a memory and having programming means for directing sequential operations, a measurement apparatus which is responsive to physical phenomena to be measured, actuator means for the measurement apparatus, controlled by the computer, for establishing in the apparatus different conditions of the phenomena to be measured, sensor means for the measurement apparatus, the output of which is relative data values which are functions of conditions present in the apparatus, a method for mathematically determining measured values of physical phenomena using curve fitting techniques comprising the steps: operating said actuator means to establish a first known condition of the phenomenon in the measurement apparatus; storing a value for said first known condition in the computer memory, storing a relative data value in the computer memory which is a function of said first known condition; operating said actuator means in response to the computer output to establish a second known condition of the phenomenon in the measurement apparatus; storing a value in the computer memory for said second known condition, and storing a relative data value in the computer memory which is a function of said second known condition; operating said actuator means for establishing an unknown condition of the phenomenon in the measurement apparatus; storing a relative data value in the memory of the computer which is a function of said unknown condition; and computing the measured value of said unknown condition; the values of said known and unknown conditions of said phenomenon each being one coordinate of different points on a curve, and said respective data values each being the other coordinate of the different points on said curve.
 22. Apparatus for measurement of physical phenomena for use with a computer having a memory, processing means and control means comprising: a measurement device responsive to a physical phenomenon to be measured; sensor means for said measurement device whose output is relative data values which are functions of conditions present in the measurement device and which may be stored in the computer memory; actuator means for said measurement device, operable in response to signals produced by the computer, for establishing in the measurement device different known and unknown conditions of the phenomenon to be measured; and a computer having a memory, processing means, and control means; said memory providing for the storing of values for said known conditions, and for the storing of relative data values for said known and unknown conditions; said computer producing said signals for controlling said actuator means; and said processing means calculating the measured values of unknown conditions established in the measurement device from said stored values and relative data values using curve fitting techniques.
 23. Apparatus as set forth in claim 22 wherein said measurement device comprises a U-tube mercury manometer for measuring gas pressures; wherein said sensor means comprises a conductive probe mounted in at least one leg of said mercury manometer and provided with a dielectric coating to define, with the mercury liquid, a capacitor for producing an electric data values responsive to the height of the mercury within the leg; and wherein said actuator means comprises a plurality of selectively operable valve means for communicating said manometer with selected known and unknown gas pressures.
 24. Apparatus as set forth in claim 23 wherein said sensor means comprises first and second conductive probes mounted respectively in the two legs of said U-tube manometer, each probe having a dielectric coaTing to define a capacitor with the mercury liquid; said first probe being shaped to define a surface area contacted by the mercury liquid which varies as a sine function during movement of the liquid from one end of the probe to the other; and said second probe being shaped to define a surface area contacted by the mercury liquid which varies as a cosine function during movement of the liquid from one end of the probe to the other.
 25. Apparatus as set forth in claim 23 including circuit means for converting the capacitance values produced by said probes to data values acceptable to the computer.
 26. Apparatus as set forth in claim 22 for measuring torque wherein said measuring device is an elongated torsion bar adapted to be deflected in response to rotational loads; wherein said sensor means includes means for detecting angular displacement between axially spaced locations on said torsion bar AS a time period; and wherein said actuator means includes a dynamometer coupled to the load end of said torsion bar for placing known rotational loads on said torsion bar.
 27. Apparatus as set forth in claim 26 wherein said sensor means further includes a pair of disc means mounted for rotation with said torsion bar at axially spaced locations thereon; signal producing means mounted on each of said disc means; a pair of signal detector means mounted with respect to the respective disc means to detect a signal from the respective signal producing means; and counter means controlled by said signal detector means for determining the time period between signals produced by the respective signal producing means.
 28. Apparatus as set forth in claim 27 wherein said signal producing means comprise permanent magnets mounted in said disc means; and wherein said signal detecting means includes magnetic pick-off devices mounted to detect the magnetic fields produced by said magnets as they are rotated past the pick-off devices.
 29. Apparatus as set forth in claim 22 for measuring temperatures wherein said measuring device comprises a sensor head enclosing, in intimate relation with each other, individual sealed quantities of at least two materials each having a known ice point, a heater element and a thermister; wherein said sensor means comprises said thermister and circuit means for converting the thermister output to data values responsive to the temperature in said head and acceptable to a computer; and wherein said actuator means comprises said heater element and a control therefore, for heating the head to a temperature above the highest ice point of said at least two materials.
 30. Apparatus as set forth in claim 29 wherein said sensor means further comprises computer means for calculating data value changes in response to time, and for comparing data value changes for successive time periods.
 31. Apparatus as set forth in claim 22 for measuring gas pressure wherein said measurement device comprises a container for a pool of liquid; float means, disposed for vertical movement within said container, having an open bottom pressure chamber communicating with the liquid surface and defining a manometer device; and conduit means communicating with said chamber; wherein said actuator means comprises valve means associated with said conduit means for selectively flowing gas into and out of said chamber; and wherein said sensor means comprises means for detecting the height of said float means relative to said container.
 32. Apparatus as set forth in claim 31 wherein said measurement device float means includes a second open bottom chamber communicating with the liquid surface defining a ballast chamber; and conduit means communicating with said ballast chamber; and wherein said actuator means further comprises valve means associated with said ballast chamber conduit means, for selectively flowing gas into and out of said ballast chamber to control the liquid column therein.
 33. Apparatus as set fortH in claim 32 wherein the cross-sectional areas of said pressure chamber and said ballast chamber are uniform throughout the height thereof and are equal to each other.
 34. Apparatus as set forth in claim 31 wherein said sensor means further comprises a resolver and linkage means coupling said resolver to said float means, wherein said resolver produces data values responsive to the height of the float means and to the pressure within the pressure chamber.
 35. Apparatus as set forth in claim 31 including means for exposing said pool of liquid and said float means to a source of reference pressure; and means communicating said conduit means for both said pressure chamber and said ballast chamber with said source of reference pressure. 